|Publication number||US7674359 B2|
|Application number||US 11/851,109|
|Publication date||Mar 9, 2010|
|Filing date||Sep 6, 2007|
|Priority date||Mar 9, 2005|
|Also published as||CA2599842A1, CA2599842C, CN101137772A, CN101137772B, DE602006002118D1, EP1859079A2, EP1859079B1, US20080053823, WO2006094814A2, WO2006094814A3|
|Publication number||11851109, 851109, US 7674359 B2, US 7674359B2, US-B2-7674359, US7674359 B2, US7674359B2|
|Inventors||Corrado Mojana, Luca Buonerba, Paolo Rossi|
|Original Assignee||Industrie De Nora S.P.A.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (16), Classifications (17), Legal Events (2)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is a continuation of PCT/EP2006/002191, filed Mar. 9, 2006, that claims the benefit of the priority date of Italian Patent Application No. MI2005A000373, filed on Mar. 9, 2005, the contents of which are herein incorporated by reference in their entirety.
The invention is relative to an electrode of cylindrical geometry for electrochemical processes, particularly a cylindrical electrode comprising a central metallic conductor with a superficial catalytic activation.
The utilisation of electrodes of cylindrical geometry is known in several sectors of electrochemistry. Cylindrical electrodes, in the majority of cases concentrically disposed inside hollow cylindrical counter-electrodes, are currently employed in electrodialysis, water electrolysis, ozone production, and other applications. The most important processes making use of cylindrical-type, mostly coaxial, electrodic geometries are for the recovery of metals from aqueous solutions and the treatment of waste water (industrial wastes, civil waters and others), for the potabilisation or purification thereof from various contaminants. The cylindrical geometries, especially on small-size electrochemical cells, offer substantial advantages particularly in terms of fluid distribution. Depending on the process under consideration, the cylindrical electrodes can be both anodes or cathodes. In the majority of cases, such electrodes are suitable for gas evolution reactions, for instance hydrogen cathodic evolution or oxygen, ozone or chlorine anodic evolution. The gas-evolving reactions, in particular the anodic ones, must be catalysed in order to take place with a sufficient efficiency. The cylindrical electrodes of the prior art, therefore, consist of a metal cylindrical conductive support (usually titanium or other valve metal, in the case of anodes) coated with catalysts usually based on metal oxides, depending on the type of the gas to be evolved and of the required potential, as widely known. The application process of the catalytic coating to the cylindrical support provides painting the latter with a precursor, and the subsequent conversion of the precursor by means of a high temperature thermal treatment (350-700° C.). The painting of metallic electrodes with precursor solutions is preferably carried out by electrostatic spraying processes. The cylindrical geometry is, in this case, less favourable than the planar one in terms of homogeneity of application. Furthermore, the catalytic coatings have a limited operative lifetime (indicatively 1 to 5 years depending on the applications). Once the original coating is exhausted, it must be completely removed by mechanical means and restored. The coating removal operation is particularly onerous for cylindrical geometries, especially for those of small size. In any case, the prolonged times required for restoring the catalytic activity of the electrodes lead to undesirable limitations to the plant operation, alternatively imposing a temporary interruption of the production, an oversize of the whole plant to allow a planned cyclic electrode reactivation, or the need of storing a remarkable amount of replacement electrodes, which is a very onerous solution from the investment cost standpoint.
It would be desirable, therefore, to provide a cylindrical electrode for electrochemical processes overcoming the limitations of the prior art. It would be further desirable to provide a cylindrical electrode allowing an increased easiness of application or of restoring of the catalytic coating. It would be still further desirable to provide an improved method for the catalytic reactivation of a cylindrical electrode in terms of process management efficiency.
In one embodiment, the invention is directed to an electrode for gas evolution comprising a conductive cylindrical core and a metal sheet or mesh fixed externally thereto and in electric contact therewith, wherein said metal sheet or mesh is an undulated sheet rolled on itself and welded along two opposed sides so as to form a cylinder of original diameter lower than that of said cylindrical core and forcedly inserted thereon.
In another embodiment, the invention is directed to an electrode for gas evolution comprising a conductive cylindrical core and a metal sheet or mesh fixed externally thereto and in electric contact therewith, wherein one side of said metal sheet or mesh is welded to said cylindrical core along a generatrix thereof, and said sheet or mesh is rolled around said conductive core.
In a further embodiment, the invention is directed to a method for the reactivation of a cylindrical electrode provided with exhausted catalytic coating, comprising inserting thereon an undulated sheet rolled on itself and welded along two opposed sides so as to form a cylinder, said undulated sheet being provided with catalytic coating.
In another embodiment, the invention is directed to a method for the reactivation of a cylindrical electrode provided with exhausted catalytic coating, comprising welding along a generatrix thereof an edge of a metal sheet or mesh provided with catalytic coating, and rolling said metal sheet or mesh around the cylindrical electrode, optionally securing the opposed edge of said metal sheet or mesh to said welded edge and/or said cylindrical electrode by means of weld spots.
The invention will be described hereafter with the support of the following figures:
The invention is relative to an electrode for gas evolution comprising a conductive core acting as current collector, whereto a detachable component is externally secured, for instance a mesh or a solid, perforated or expanded sheet, made of conductive material. In one embodiment, the detachable component is provided with a catalytic coating and constitutes the active element of the electrode. The electrodic geometry of the invention is particularly suited to the construction of anodes for oxygen, ozone or chlorine evolution in electrometallurgical or water-treatment processes. In this case, the conductive cylindrical core is advantageously made of a valve metal, in the most typical case titanium. The cylindrical core may have any size, the most typical diameter being comprised between 1 and 25 cm, depending on the application. The detachable component comprises a metallic mesh or sheet, which may be advantageously made of the same material of the conductive core, having thickness comprised between 0.3 and 0.8 mm even though other thicknesses are equally possible.
In another embodiment, the invention is relative to a method for the reactivation of a cylindrical anode provided with an exhausted catalytic coating, comprising the application of a detachable element provided with a catalytic coating externally thereto.
A mesh (201) provided with a catalytic coating is flag-welded along the generatrix of the cylindrical conductor (101). The figure shows the junction of the two pieces as a continuous weld (300), for instance obtainable via laser, but also different types of welding such as spot welding are possible. The mesh (201) may also comprise an expanded or perforated sheet or a solid sheet.
The following example is included to demonstrate particular embodiments of the invention. It should be appreciated by those of skill in the art that the techniques disclosed in the examples which follow represent techniques discovered by the inventors to function well in the practice of the invention. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention.
A titanium cylindrical anode for a cell employed in copper electrodeposition tubular cells disclosed in U.S. Pat. No. 6,451,183, consisting of a 15 cm thick titanium hollow cylinder, was activated with a titanium and tantalum oxide-based coating (16 g/m2 overall) over a titanium and tantalum oxide-based intermediate layer, as known in the art. The anode was subjected to a standard oxygen evolution test in 5% sulphuric solution at a temperature of 25° C. and at a current density of 500 A/m2. In the course of eight hours of test a stable voltage of 3.30 V was detected (electrode according to the prior art).
An electrode according to the invention was prepared making use of an identical titanium rod free of catalytic activation, whereto a 0.5 mm thick titanium mesh activated with the same composition of the previous sample according to the prior art was secured, utilising the configuration shown in
The electrode was subjected to the same oxygen evolution test of the previous sample, at identical process conditions. In the course of eight hours of test, a stable voltage of 2.90 V was detected (electrode of the invention).
It was thereby shown how the electrode of the invention, besides solving the inconveniences of the prior art mainly associated with the reactivation of exhausted cylindrical electrodes in a very practical fashion, is also capable, probably due to the greater exposed surface, to operate at a higher energy efficiency (lower voltage) corresponding to a higher expected lifetime.
Although the disclosure has been shown and described with respect to one or more embodiments and/or implementations, equivalent alterations and/or modifications will occur to others skilled in the art based upon a reading and understanding of this specification. The disclosure is intended to include all such modifications and alterations and is limited only by the scope of the following claims. In addition, while a particular feature may have been disclosed with respect to only one of several embodiments and/or implementations, such feature may be combined with one or more other features of the other embodiments and/or implementations as may be desired and/or advantageous for any given or particular application. Furthermore, to the extent that the terms “includes”, “having”, “has”, “with”, or variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.”
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|U.S. Classification||204/284, 204/280, 204/260, 204/272|
|International Classification||C25B11/02, C25B11/03|
|Cooperative Classification||C25C7/02, C02F2001/46152, C25D17/12, C25B11/02, C02F1/4672, C02F1/46109|
|European Classification||C25D17/12, C25C7/02, C02F1/461B2, C25B11/02, C02F1/467B|
|Sep 10, 2007||AS||Assignment|
Owner name: INDUSTRIE DE NORA S.P.A., ITALY
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:MOJANA, CORRADO;BUONERBA, LUCA;ROSSI, PAOLO;REEL/FRAME:019803/0384;SIGNING DATES FROM 20070704 TO 20070706
Owner name: INDUSTRIE DE NORA S.P.A.,ITALY
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:MOJANA, CORRADO;BUONERBA, LUCA;ROSSI, PAOLO;SIGNING DATES FROM 20070704 TO 20070706;REEL/FRAME:019803/0384
|Mar 14, 2013||FPAY||Fee payment|
Year of fee payment: 4